The present invention relates generally to surge protection devices. More particularly, this present invention pertains to surge protection devices for LED driver systems and a method for alerting users as to the need to replace failed surge protection components.
LED technology has changed the way the world sees lighting. The various benefits of LED lighting, e.g. their long life, high efficacy, green energy, high level of flexibility and dimmability call for perfectly matched power supplies (LED drivers). In order to leverage the benefit of long life of LEDs, LED drivers must also be designed to be robust under lighting power surge conditions. Electronic light emitting diode (LED) drivers are subject to significant surges on the input lines. In many conventional applications, electronic LED drivers, and the LEDs themselves, are protected by surge suppressor circuits which are connected in parallel with the inputs of the LED drivers. Such surge suppressor circuits may also conventionally include clamping devices such as metal oxide varistors (MOVs). In practice, these devices may be provided with a rated working voltage slightly higher than a maximum AC input voltage specified for the respective LED driver. For example, an MOV rated for 320 Vrms may be used in 120/277 Vac input applications. The clamping devices in such configurations will remain non-conductive during normal operation, and can therefore operate continuously across AC power lines as the voltage across the devices is well below their respective “clamping voltage.”
However, the performance of surge suppressors containing MOVs degrades with each surge event, or may even be destroyed entirely in the event of a lightning strike or the like wherein the energy involved from AC lines to earth ground (GND) is typically many orders of magnitude greater than the device can reasonably handle. Such uncontained damages to the surge protection devices are usually in violation of many safety standards such as UL1449.
In addressing these problems, it is further known to use an internally thermally fused surge protection device, whereas in the event of overheating due to the abnormal overvoltage during a lightning strike or the like, the thermally activated element in the surge protection device opens and protects associated MOVs from being violently damaged. However, one drawback to this solution is that there is no apparent indication to users that any of the device components have failed. Any large successive voltage surges can accordingly damage the entire LED driver, an expensive prospective replacement.
It would be desirable to provide an inexpensive method for an operator to determine the status of a surge suppression system that is usually inconveniently located, e.g., at the top of a pole or ceiling of a warehouse. This is especially problematic wherein determining system status requires a physical measurement.
It would further be desirable that indication of a failed surge suppressor can allow replacement of an inexpensive component in an expensive system before damage occurs to the remaining system.